The present invention relates to a method and apparatus for the non-invasive ultrasound body contouring of a subject, particularly for the treatment of fat deformities by lysing adipose (fat) tissue.
Three methods are currently available for the treatment of fat deformities: Suction Assisted Lipoplasty [SAL]; Ultrasound Assisted Liposuction [UAL]; and External Ultrasound Assisted Liposuction [E-UAL].
These procedures are skill dependent such that the results depend primarily on the skill of the surgeon. The surgeon marks the areas to be treated on the skin in a manner resembling a topographic map; the higher innermost areas have more fat, and lower outer areas have less fat.
In SAL, a cannule is inserted through a small skin cut into the adipose tissue and the fat is suctioned by negative pressure applied through the cannule by a pump. The cannule is moved back and forth in different tissue levels covering the volume to be suctioned. The fat is torn and evacuated at the same time. Usually more then one skin cut is needed in each area to achieve satisfactory result, and to avoid tunneling under the skin.
This procedure is nonselective and tears also blood vessels, small nerves, and connective tissue. Hemmatomas and hypo-sensation in the treated areas are unavoidable side effects. Following the surgery, the patient is usually dressed with a pressure garment for 4-6 weeks. Pain is common and generally takes a few days to subside. The procedure can be carried out under local or general anesthesia in an operating room or office environment. However, most of the procedures are performed under general anesthesia because of the discomfort to the patient. The procedure lasts up to 3-4 hours, depending on the amount of fat to be suctioned and on the surgeon""s skill. The volumes cleared in one session are usually 2-5 liters.
UAL was introduced by Zocchi, in 1991. Here, too, the same saline solution is first injected into the fat tissue. The cannule used in UAL has an ultrasonic probe at its tip. When energy is applied, the tissue next to the tip is destroyed by the xe2x80x9ccavitational effectxe2x80x9d as described more particularly below. The wet environment achieved by injecting the saline solution is mandatory for the cavitation effect to occur. The fat can be evacuated by the same cannule or by a different one after the ultrasonic lipolysis was accomplished. It is claimed to be selective to the fat. However, if the physician does not move the cannule constantly, the tissue next to the tip can be xe2x80x9cburnedxe2x80x9d, and skin, muscle or bone tissues can be damaged. Third degree skin burns are a notorious complication of the procedure. Moreover, the movement of the canule through the adipose tissue disrupts blood vessels, nerves, and connective tissues as in the SAL procedure. The ability to evacuate large volumes is the main reason for using the UAL technique. Physicians have reported volumes reaching 15-27 liters of fat suctioned in one session. The skin is claimed to retract better after UAL compared to SAL, leaving less folds post treatment.
E-UAL is a newer technique. It employs the usual SAL technique but adds a treatment with a therapeutic ultrasonic transducer usually used to relieve pain and joint problems. The therapeutic ultrasound is applied after a tumescent solution is injected. The claimed advantage of the procedure is the relative ease of SAL after ultra-sound is applied. However, the energy is non-focused at 1 MHz, and therefore heating is the mode of action. Since energy is applied to the skin and underlying tissues equally, overheating may occur. A known side effect is hyper-pigmentation of the skin due to a healing process that takes place at the heated area. Moreover, pain and discomfort are common. Rohrick et al, in Plastic and Reconstruction Journal 105:2152, 2000, showed that the cellular disruption after E-UAL is similar to the traditional SAL. Otherwise this procedure is equivalent to SAL.
A tissue can be non-invasively exposed to ultrasonic energy in a focused or a non-focused manner. When a non-focused transducer is used, all tissues between the transducer, and up to a certain fading distance where energy levels are lower than the therapeutic threshold, are exposed to the ultrasonic energy. When focused ultrasound is used, only the tissue at the focal range of the transducer is specifically affected while all other tissues, between the transducer and the focus or beyond, are spared.
There are two modes in which ultrasonic energy interacts with tissues; (1) by heating, and (2) by cavitation.
Heating is non-specific. There is no tissue differentiation in the heating process; all tissues within a certain spatial radius are affected.
Cavitation is a physical phenomenon in which low-pressure bubbles are formed and then collapse in a liquid. The cavitation phenomen depends on specific tissue characteristics when employed in a biological environment. This enables tissue differentiation for destruction. That is fat cells can be destroyed, while blood vessels, peripheral nerves, skin, muscle and connective tissue within the ultrasonic focus, as well as neighboring tissues such as listed above outside the focus, will remain intact.
U.S. Pat. No. 6,113,558, in which one of the joint inventors is the inventor in the present application, describes both an invasive method and apparatus, and a non-invasive method and apparatus, for using ultrasound devices for cavitationally lysing tissue for ablating material obstructing blood vessels. U.S. Pat. No. 5,827,204 discloses a multi-frequency ultrasound cavitation technique for dissolving thrombi, promoting blood clotting, and destroying malignant and benign tumors in living tissue. U.S. Pat. No. 5,143,063 discloses a technique for focussing radiant energy (the sole described example utilizing microwave) to remove adipose tissue. U.S. Pat. No. 5,219,401 discloses a technique for generating gas bubbles, e.g., by injecting a precursor of gas bubbles, and then provoking in implosion by high power acoustic waves to selectively destroy tissue. U.S. Pat. No. 5,419,761 discloses a liposuction technique including the insertion of a tube and the production of ultrasonic cavitation at the distal end of the inserted tube to remove adipose tissue. U.S. Pat. No. 5,618,275 discloses a method of penetrating a therapeutic agent through the skin by ultrasonic waves producing cavitation. U.S. Pat. No. 6,039,048 discloses a technique using thermal energy rather than cavitational energy, and which acts on connective tissues rather than fat tissues.
None of the foregoing techniques appears to be completely satisfactory for producing lysis of adipose tissue without damaging non-adipose tissue in a non-invasive manner.
An object of the present invention is to provide a non-invasive method and apparatus for using ultrasonic devices for the treatment of fat deformities by producing lysis of adipose tissue without damaging non-adipose tissue.
According to one aspect of the present invention, there is provided a method for producing lysis of adipose tissue underlying the skin of a subject, comprising: applying at least one ultrasonic transducer to the subject""s skin to transmit therethrough ultrasonic waves focussed on the adipose tissue; and electrically actuating the ultrasonic transducer or transducers to transmit waves of sufficient intensity to cause cavitation and lysis of said adipose tissue without damaging non-adipose tissue.
According to further features in the preferred embodiments of the invention described below, the electrical peak output power is preferably from 100 to 750 watts, more preferably from 150 to 350 watts; the periodic ultrasonic waves have a pulse length of 0.80-4.0 ms a frequency of 150-500 Khz, preferably 250 Khz, and a repetition period of 5-100 ms.
As will be described more particularly below, such an ultrasonic transducer may be slid over the skin to destroy the adipocytes membranes and nuclei of the adipose tissue, without damaging neighboring tissues, such as connective tissue, the skin, blood vessels, peripheral nerves, muscle fibers or bone. Also, the procedure can be carried out in any office setting without the need for an operating theatre and anesthesia.
According to another aspect of the present invention, there is provided apparatus for use in producing lysis of adipose tissue underlying the skin of a subject, comprising: a focussing-type ultrasonic transducer or transducers for application to the subject""s skin; and an electrical signal generator having a controller therein for energizing the ultrasonic transducer to generate, and to transmit through the subject""s skin, periodic ultrasonic waves producing cavitational lysis of the adipose tissue without damaging non-adipose tissue.
Further features and advantages of the invention will be apparent from the description below.